Canine distemper (CD) is a highly infectious, febrile disease of dogs and other carnivores (Fenner, et al., 1987, Veterinary Virology, Academic Press, Inc., pp. 485-503). The mortality rate is high, ranging between 30 and 80 percent. Dogs survived often have permanent central nerve system damage (Fenner, et al., 1987). The established etiology of CD is infection by a member of the Paramyxovirus family, morbillivirus genus known as CD virus (CDV). In general, Paramyxoviruses are enveloped viruses containing an 18-20 kb single stranded RNA genome of negative polarity. The genome encodes 5 to 7 structural proteins including a fusion (F) and either a hemagglutinin-neuraminidase (HN) or hemagglutinin (HA) glycoprotein. The membrane glycoprotein hemagglutinin (HA) is responsible for hemagglutination and attachment of the virus to the host cell, and the fusion glycoprotein (F) causes membrane fusion between the virus and the infected cell or between the infected and adjacent uninfected cells (Graves et al., 1978, Virology 86:254-263). For CDV, both F and HA glycoproteins are found present in the viral envelope and on the surface of infected cells. By inference from analyses with other morbillivirus members, the CDV F and HA glycoproteins appear important for CDV infection and its immunobiology (Diallo A., 1990, Vet. Micro. 23: 155-163). Poxvirus based recombinant CDV vaccines have been developed to protect and treat dogs (U.S. Pat. No. 5,756,102). U.S. patent application Ser. No. 09/232,477 disclosed DNA plasmid based vaccines expressing CDV antigens.
Granulocyte-macrophage colony-stimulating factor (GM-CSF) was first discovered in 1977 (Burgess et al., 1977, J. Biol. Chem. 252:1998-2003). GM-CSF has many physiological roles. In particular, GM-CSF stimulates the production, the development and the formation of colonies of granulocyes, macrophages, eosinophils and megakaryocytes. (Dy M., in “les Cytokines” Cavailon 1995 ed. Masson, Paris, France, 43-56). GM-CSF induces in particular a macrophagic cytotoxocity, stimulates antibody-dependent cytotoxic activity (ADCC) and the recruitment of leukocytes at the level of the sites of inflammation.
The sizes of the nucleotide sequences encoding the known GM-CSFs from various species vary from 381 to 432 nucleotides. The human and murine nucleotide sequences have a degree of homology of 69%. The degree of homology is 54% at the level of the amino acid sequence (Cantrell et al., 1985, Proc. Natl. Acad. Sci. USA 82:6250-6254). An equine GM-CSF was identified which has a size of 144 amino acids (U.S. Pat. No. 7,250,161). Two canine GM-CSFs were identified in U.S. Pat. No. 5,702,919 and U.S. Pat. No. 5,606,024, which have 127 amino acids and 174 amino acids respectively.
The administration of heterologous GM-CSF does not make it possible to obtain an optimum adjuvant effect, in particular a stimulation of the activity of the haematopoietic cells and a substantial increase in the immune response.
There is thus a general need for an improvement in efficacy and safety of the CDV vaccines and for more effective protection in field conditions.
The invention provides a solution for optimizing the immunological effect of caGM-CSF while retaining high safety for the vaccinated dogs.